a) Field of the Invention
The present invention relates to a lens drive unit that is used for a relatively compact-sized camera and so on, such as a camera of a camera-equipped cell-phone and so forth.
b) Description of the Related Art
When a cellular phone equipped with a camera is used, the camera user often takes a photo of the user's own face and/or any of other photographic subjects at a close distance while holding the cellular phone in a single hand. Therefore, quite a few of the shooting lens systems used in this type of camera are provided with a close-up shooting function. In the case of such a shooting lens system provided with the close-up shooting function, lens positions for normal-distance shooting and close-up shooting, i.e., macro shooting, are different from each other. Namely, the lens position for close-up shooting is slightly closer to the object of shooting for a certain distance than the lens position for normal-distance shooting.
For this reason, the shooting lens system of this type is equipped with a drive unit for moving the lens between the position for normal-distance shooting and the position for macro shooting. The drive unit is operated by changing the switch status to move the lens between the two positions described above. However, for a mobile device such as a cellular phone and so on, it is difficult to use a motor as the drive unit because of compact design and weight saving of the mobile device.
Therefore, conventionally it is proposed to use a lens drive unit of a magnetic drive type, which includes: a cylindrical lens holder to support the lens; a ring-shaped magnet placed around the outer circumference of the lens holder; and a drive coil facing to the magnet; wherein the lens holder supporting the lens is directly moved in an optical axis direction, not via any transmission mechanism, by controlling an energizing operation for the drive coil, and then the lens holder is magnetically retained there. (Refer to Patent Document 1: Japanese Unexamined Patent Publication (Kokai) No. 10-150759).